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### Phase Slope Distance Calcuation

After trying to implement IFFT algorithms for phase-based ranging, as outlined in this very interesting and descriptive blog post; I've been getting horrendous results (orders of magnitude inaccurate),...
70 views

### Why does this RLC behavior differ from what equations predict?

In order to better understand RLC behavior under current sources, I constructed the simple circuit below and attempted to analyze it. However, my equations do not agree with simulation results. The ...
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33 views

### Phase-Based Ranging

I've been reading a lot about Phase-Based Ranging (PBR), and it's all starting to become very intuitive. BUT; There is one technical, but extremely important, detail that seems to escape me. When the ...
63 views

### Are these levels of RF radiation harmful?

I live on the top floor of a building that has four 5G antennas on the roof. The house is curved, and from my viewpoint, I can partially see one of the antennas pointing towards me. Curious about the ...
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56 views

### Prime operator for sinusoidal testing function in self-term approximation for Thin Wire using Method of Moments (MoM) $s_m^{'}(x_p)$?

I am implementing thin wire method of moments using W.Gibson's "Method of Moments in Electromagnetics". The approximation for self-term using piecewise sinusoidal basis function is given as ...
1 vote
23 views

### Synchronous phase value for CERN LHC [closed]

How to find out that the value of the synchronous phase for CERN LHC in the case where beams undergo collision, and the RF cavities provide only longitudinal focusing with no net acceleration.
1 vote
28 views

### Slice selection in MRI

Studying MRI, I found that excitation is done by applying B1 (RF) and Gz simultaneously. But, I think that if those are applied at same time, slice selection cannot be done correctly because Gz will ...
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73 views

I have recently obtained a job in the field of radio frequency antennas and satellites, and I am interested in delving deeper into the subject. Could you recommend any books that cover these topics ...
82 views

### Why is 180 degree pulse applied after half echo time (TE) in Spin Echo sequence?

The definition of Echo Time from Radiopaedia: The echo time (TE) refers to the time between the application of the radiofrequency excitation pulse and the peak of the signal induced in the coil. It ...
85 views

### Gravitational waves vs ULF Radio waves

During the recent merger of two Neutron stars the lead up to the merger was detected as gravitation waves. This was the merger of two spinning bodies that had very strong magnetic fields and they were ...
55 views

### Is the Fourier Transform a reliable way to infer the physical phenomena producing an RF signal?

Consider the following thought experiments: Scenario 1: A person standing far away shines 3 light beams at you, each beam having a narrow spectral distribution centered around different frequencies F1,...
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### Can I recover the physical wavelengths present in a light source from a time-series measurement of its amplitude?

Consider a mixture of different wavelengths being emitted from the same point (ex: a star). This light consists of a mixture of wavelengths and intensities at each wavelength. When measuring the ...
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### What exactly decides the TTC frequency selections of X-band for deep space missions, C band for geostationary , and S band for LEO missions?

Data rates are higher in X-band, but considering free space path loss and atmospheric attenuation(diffraction I'm assuming is significant here), won't lower frequencies stand a better chance? Again, ...
63 views

### How to measure time varying electric field strength accurately in space and time?

I would like to know of any techniques that can be used to measure the electric field strength precisely and accurately in both time and space. I know that there will be physical/ practical ...
• 113
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### Question about CPU manipulation with RF waves [closed]

Is it possible that by sending a specifically modulated RF wave, you can manipulate the flow of electricity to the CPU, and maybe cause binary code Execution? Like typing something like Hello?
53 views

### How to increase the angle of light (without going from a higher to lower index of refraction)?

I would like a device to spread out/increase the angle of rays in a light source. In other words, I would like to reproduce the behaviour of light traveling from an area of higher to lower index of ...
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10 views

### Does the RF magnetic field have to be uniformly constant for a coherent EPR signal

Consider a loop gap resonator for electron paramagnetic resonance which has static (but sweepable) magnetic field in one direction, "x", and a GHz RF magnetic field in a direction "z&...
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1 vote
48 views

### When does Lorentz reciprocity not apply to an EM system?

I'm trying to understand the limits of when Lorentz reciprocity does and doesn't apply to a given system. I know that it only applies to linear systems, but based on a couple of examples I believe ...
• 113
1 vote
65 views

### Is there an intuitional way to tell which physical quantities are angular frequency and which are frequency?

Such as the natural linewidth is defined to be angular frequency, while the absolute frequency of laser is frequency. By far I haven't found a good way not to learn it by roting. Would anyone be ...
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1 vote
47 views

### How a does a RF magnetic field interact with trapped atoms in evaporative cooling?

In the paper “Evaporative Cooling of Trapped Atoms,” [Advances in Atomic Molecular And Optical Physics 37, 181–236 (1986)] by Wolfgang Ketterle and N. J. Van Druten, they claimed the matrix element ...
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656 views

### Impedance at Feed Point and End of Antenna

Watching this pretty great video from 1947 about antenna fundamentals. I have a question about one part of it though. The video states that the impedance at the feed point of the antenna is 72 ohms, ...
121 views

### Antennas and Wavelength

I'm clearly missing something here, but I'm trying to grasp basics of how antennas work. Relating it to standing waves on a string of length L, the lowest frequency possible is a wavelength of 2L, due ...
1 vote
29 views

### Wireless Power Transfer Modelling

I am trying to develop an analytical model for RF wireless power transfer from an external antenna to an implant antenna, embedded inside layers of lossy tissue. The external antenna will be ...
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1 vote
33 views

### How would we create a device to detect communication using the x-ray and gamma bandwidth? Like a radio. But x-ray gamma spectrum [closed]

I realize the dipole would have to be small enough (in the nucleus of an atom range) and we don't have any mechanism that is small enough to demodulate the frequencies at this rate. But is there some ...
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1 vote
193 views

### How does one pick Echo time (TE) in MRI machine?

The definition of echo time (TE) in MRI is the time difference between a 90-degree RF signal and the echo peak, which feels like an intrinsic property of the proton. How can we even control how long ...
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### Mathematical Modelling of Wireless Power Transfer

I am trying to understand the interaction between a transmitting antenna with a certain transmitting power (denoted PTX in the diagram) and how the radiation pattern of the TX antenna is affected by a ...
• 11
358 views

### How does radio wave get reflected?

Actually recently I posted a question in h-bar ($\hbar$) relates to radio wave reflection from mirror, and one of the user replied that it can't, only ionosphere can reflect it, so my question what is ...
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198 views

### Feynman physics on least time of light

What does light checks all paths mean by Feynman? Especially the statement is labeled by yellow. Why there is only one path that leads radiowaves to D’? And how wave check all paths, that is, why it ...
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1 vote
56 views

### What is physically happening in a medium in which an evanescent wave is propagating?

Let's consider for instance a metal, for which the dielectric function reads: $\epsilon = 1 - \frac{\omega_{p}^{2}}{\omega^{2}}$ where $\omega_{p}$ is the plasma frequency. The dispersion relation for ...
37 views

### Can radio waves with multiple frequencies have the same power?

I was watching data from a spectrum analyzer that shows the frequency of the wave and its power in dBm. I noticed that all frequencies were operating at the same power; however, I don't understand how ...
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29 views

### Interferometry maximum wavelength for a set of baseline lengths

I am trying to understand phase ambiguity resolution for interferometry. Unfortunately, all I have are old power points and not really any notes or textbooks on the subject. I have found in a power ...
1 vote
36 views

### Is there an optical/electromagnetic equivalent to the mechanical lever?

From Wikipedia: "Levers can be used to exert a large force over a small distance at one end by exerting only a small force (effort) over a greater distance at the other." Is there any ...
82 views

### Cryogenic and vacuum safe cable labeling or tagging

Not the most in depth of physics questions, yet this feels like the right community for trying to crowd-source this type of expertise. Essentially it is a question for those of you experienced with ...
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49 views

### Mechanism of NMR

I am doing research into NMR right now in several different sources, and it seems as if there are two competing models which are used to describe how radio waves can impact nuclear spins. The first ...
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1 vote
79 views

### Implementation Question about Thin Wire Method of Moments

I am currently trying to implement a simple $1 \textrm{D}$ thin-wire method of moments code in Python to practice E&M and numerical methods. I am following Gibson's "The Method of Moments in ...
59 views

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1 vote
25 views

### Is there any mathematical model of how does rain & other weather conditions impact the radio link?

I'm looking through UAV radio-communication process and wondering if there are any formulas, describing how does the air pressure and weather itself (rainy & snowy conditions) affect the radiolink ...
42 views

When a far field propagated radio wave encounters an obstacle such as a mountain does the radio wave actually bend around the mountain? In other words should my receiving antenna on the other side of ...
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1 vote
309 views

### Superposition of EM waves and "magic" behind tuned receiver circuit

I'm struggling to understand how the receiver circuit (eg. FM radio) is able to extract a particular frequency out of the sum of all received frequencies by its antenna? I've checked dozen of websites,...
23 views

### Frequency upconversion of pulses shorter than 1 IF period

I have a rather elementary frequency upconversion/mixer question, perhaps so simple that it does not warrant a real question but rather just a reference to a website/tutorial (that I have not been ...
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2k views

### How are sidebands generated in an AM signal?

I can't understand how sidebands get generated, even after reading this wikipedia page: https://en.wikipedia.org/wiki/Sideband#Amplitude_modulation This is how I picture Amplitude Modulation in its ...
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64 views

### Scattering off upside-down parabolic reflector (radio frequency)

Suppose I have a steel frame parabolic reflector with a handful of steel wire supports. The size is approximately 10m high and 20m in radius. Assume the gaps in the triangular trusses are roughly 3m. ...
604 views

### Why is a magnesium flame changing color in an electromagnetic field?

On YouTube I have seen someone build a RF emitter (probably in the 10 MHz range with about 5000 Watts) and then use it to ignite magnesium strips. Magnesium usually burns with a bright white flame in ...
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